This invention relates to a method of operating an actuator which is used to open and close valves in a pipeline and more particularly to the avoiding of pressure surges and resonances when the valve is closed.
In the water supply sector there is the problem, in particular but not exclusively in the remote water supply sector, that when valves are closed, as a result of the water columns in the pipeline, which are often several kilometers long, pressure surges occur, which can lead to the pipeline bursting. This problem becomes pressing during disasters, in which the pipeline has to be shut off as quickly as possible.
From the catalogue number DO 01.01.004D/1.97, page 22 from AUMAxe2x80x94Werner Riester GmbH and Co. KG, it is known to operate the drive motor of the actuator in a clocked manner, starting from the open state of the valve and as the closed state of the valve is approached. In this case, the drive motor of the actuator is switched ON and OFF periodically in accordance with predefinable run and pause times.
Although, with the known solution, it is possible to limit the intensity of the pressure surges, it is not possible to avoid the pressure surges. Furthermore, by means of the clocked operation of the drive motor, periodic pressure surges are produced in the pipeline, which are amplified by the excitation of resonance and can lead to the pipeline bursting. Furthermore, the higher mechanical load on the actuator and the valve as a result of the clocked operation promotes wear and is therefore disadvantageous.
In order to keep the relative adjustment travel jump and therefore the first pressure surge as low as possible, the clocked operation must be started as early as possible. The resulting prolongation of the actuating time until the valve is closed completely is viewed as disadvantageous in disasters, in which the pipeline must be shut off as quickly as possible.
The invention is therefore based on the object of specifying a method of operating an actuator which avoids pressure surges and resonances which endanger the pipeline and, nevertheless, permits a short actuating time.
The invention is based on an actuator, known per se, for opening and closing, a so-called OPEN/SHUT drive, a valve in a pipeline, the valve having a movable actuating element which is operated by the actuator.
The closing operation of the valve is subdivided into at least two closing phases. During the first closing phase, the actuating element is moved at maximum actuating speed down to a predefinable position of the actuating element, starting from the open state of the valve.
According to the invention, from this predefinable position of the actuating element, in the second closing phase, the actuating speed of the actuating element is reduced continuously and steplessly with a predefinable gradient.
During the closing action, the pressure in the pipeline to be shut off rises in proportion to the actuating speed. As a result of the continuously stepless change in the actuating speed with a predefinable gradient, pressure surges in the pipeline to be shut off are avoided. For this reason, and because of a lack of periodicity in the change in the actuating speed within an actuating operation, the excitation of resonance in the pipeline is also avoided.
As a result of the continuously stepless change in the actuating speed, the armature is closed in a short actuating time, utilizing the permissible pressure in the pipeline.
According to a further feature of the invention, the actuating speed in the second closing phase is reduced to a predefinable constant speed value. In a following third closing phase, this reduced actuating speed is maintained until the valve is closed completely.
As a result, with early restriction of the actuating speed as a function of the parameters of the pipeline, the closing of the valve is achieved with a minimum actuating time.